A noncontact support surface includes an arrangement of pressure nozzles and vacuum nozzles on the surface of a pressure-vacuum (PV) stage. The pressure nozzles are connected a pressure source so as to cause an outflow of air from the PV stage. The vacuum nozzles are connected to a vacuum source such that air is sucked into the PV stage via the vacuum nozzles.
The outflow of air through the pressure nozzles and the inflow of air through the vacuum nozzles may create an air cushion that is capable of supporting an object (e.g., a flat object). The outflow and inflow may create a fluidic spring effect that resists any change in distance between the object and the surface of the stage. Thus, the noncontact support surface may support the object at a fixed distance from the stage surface. The stage may support the object from below or from above.
Interruption of air flow through one or more nozzles may decrease the uniformity of the air cushion. Thus, a blocked nozzle may affect the distance between the object, or a portion of the object near the blocked nozzle, and the stage surface. A deviation of the distance from an expected distance could adversely affect the quality of a measurement or process that is performed on the object.